The invention is useful in machine knitting on a weft knitting machine having independently operable needles disposed in at least two needle beds, for example, a flat V-bed machine producing a mainly double jersey structure. In such machines, the width of the knitted fabric is restricted by the maximum number of needles available for forming a course across the machine bed.
Three-dimensional fabric structures for covering three-dimensional objects have in the past been produced by weaving and knitting shaped parts and panels and sewing them together.
More recently, it has been found possible to knit one-piece upholstery fabric, which removes the need for sewing portions together, and has the desired shape to serve as covers for the base and back cushions for vehicle seats; see, for example, British Patent 2,223,034. A problem that has arisen with the continuous knitting of three-dimensional fabric structures is that it has hitherto been impossible without specialized machines to knit fabrics which include vertically orientated pouches or protrusions, that is, protrusions which are orientated in a substantially wale-wise or vertical direction. This problem arises because a pouch orientated in a vertical direction has transverse surface dimensions which are longer than the distance across the width of the available needle bed. This is analogous to distances on the ground in mountain being further than the measured flat map distances.
Another consideration in making knitting patterns is that the edges-to-be-joined should have the same length, and any angle between them should be equally bisected by a horizontal line. Shaping can be achieved with edges of different lengths and asymmetrically bisected angles but the joins will be distorted.
Furthermore, in the preparation of the pattern, the angle between edges-to-be-joined should not be too large, and it is generally considered that a maximum angle should lie in the range of 90.degree. up to 135.degree., depending on the application. British Patent Application GB-A-2,223,036 discusses this problem.